This critically important core provides routine and consistent analysis of spleen cells, cervical lymph node cells, and resident as well as inflammatory cells derived from the CNS. As noted in the individual projects, precise analysis of the cells infiltrating the CNS during infection, as well as the resident CNS cells (oligodendroglia, astrocytes and microglia) are key components of the overall program. This includes measurement of surface markers, immune modulatory molecules, and cytokines expressed during immune activation by both resident and infiltrating cell types. Precise identification and separation of cell types is required for both acquisition and analysis and cell purification by sorting. This Core will provide quality control for efficacy and purity of various cell sorting strategies required for each project. This Core will furthermore interact with the Animal Core (Core B) by confirming reconstitution of kjone marrow chimeras and genetic phenotypes in the breeding colonies. The major functions are thus to: 1) provide routine acquisition and analysis of cell composition and their phenotypic changes in various tissues; 2) purify cells from various mouse tissues for gene profiling and immunological assays in vitro; 3) verify the efficacy of bone marrow reconstitution; 4) analyze PBMC for genotyping; and 5) provide quality control for cell separation and purity. Performance of all these tasks fulfills essential functions for all three projects. Core B is critical to accomplishing the overall scientific goals of the entire project.